This invention is related to seat assemblies for ball valves which are constructed so that the face seal is removable. More specifically this invention is related to a ball valve seat assembly which has a seat ring that mounts in the valve body and a face seal insert which is removably mounted in the seat ring.
In the prior art numerous valve seat constructions are known which have removable face seals, however, in these constructions the face seal is merely one side of a resilient seat ring. In these constructions the complete seat is removed and replaced for repair of the valve. One example of this is the patent of Freeman et al, U.S. Pat. No. 2,945,666 issued July 19, 1960, and another example is the patent of Lowery, U.S. Pat. No. 3,226,080 issued Dec. 28, 1965. Another typical type of seat construction is a metallic seat ring which has a non-metallic face seal element clamped, crimped, or otherwise secured such that replacement of the seal element requires also the replacement of the supporting ring. One example of this construction is the patent of Colby et al, No. 3,460,802 issued Aug. 12, 1969. Each of these prior art constructions have their own peculiar disadvantages. In the case of the completely elastomeric seat ring, it is generally used only in the smaller sizes of valve such as (4) inches, approximately (100) millimeters and in relatively low pressure applications because of physical characteristics of the elastomer. In the other construction where the resilient seal element is physically retained by the metallic seat ring, this is generally used in the higher pressure applications and usually in larger sizes. The disadvantage in this type of seat is in the expense of repairing the seat assembly. Generally in this second type only the seal element wears out and needs to be replaced, however, the seal element and the seat ring both must be replaced due to the unit like construction.